Stroll recorded a 1:36.302s inside the final minute of the session to head Piastri by 0.3s after a slightly limited hour of running.
A grass fire partway through the session briefly halted proceedings but ultimately didn’t cost teams too much during what was a critical hour of running.
Results: Chinese GP, Practice 1
With Sprint Qualifying to follow, and no further practice sessions this weekend, teams ran mixed programmes as they gathered the date they needed for the remainder of the weekend.
That saw some run qualifying laps midway through, and others log their fast times on hard tyres with a view to saving new rubber for the qualifying sessions to come.
Despite the limited practice running, there was no stampede out of the lane as the session began.
Instead, only half a dozen cars fed out in the opening couple of minutes, including local favourite Zhou Guanyu for Sauber.
A critical aim of the session was understanding the track surface, which has historically been hard on tyres.
F1 hadn’t visited the Shanghai International Circuit in five years, during which time new regulations were introduced that changed the aerodynamic philopshy used by cars.
Understanding the demand on tyres was crucial, along with establishing ride heights on a surface that had been given a coating of bitumen paint rather than a resurface.
All three compounds were in use; the medium tyre favoured by Red Bull Racing as Max Verstappen went fastest with a 1:39.497s – some five seconds off the best time set in the 2019 Chinese Grand Prix (set by Pierre Gasly for Red Bull Racing).
Conditions were not easy, with a number of drivers having moments; Lewis Hamilton had a wild slide through Turn 1, while Sergio Perez had a brief off-track moment.
A key difference to the circuit from 2019 to now is the addition of gravel on the outside of the final corner, offering a strong incentive against attacking the corner as drivers once did.
After 10 minutes, Red Bull Racing sat atop the timesheets, with Verstappen fastest in a 1:39.110s and Perez only 0.049s slower.
Neither Ferrari driver had set a time to that point, George Russell for Mercedes also without a time to his name.
After 14 minutes of running, the red flag was shown for a grass fire on the apex at Turn 7 – likely caused by a spark from a car as it bottomed out around the left-hander.
Running resumed after only five minutes, limiting the disruption to teams.
Russell finally recorded his first timed lap with 25 minutes complete, logging a 1:41.149s to remain slowest.
The Mercedes driver was on the hard compound tyres, as was Hamilton who was only 17th fastestst with seven laps under his belt.
Hamilton then found himself forced into the pit lane as he attempted to negotiate his way through traffic at the final corner.
Having let Verstappen through on the back straight, he closed the door on Hulkenberg at the penultimate corner before encountering Oscar Piastri at the final corner, which saw the Mercedes drier pinch a brake and skate into the pit entry.
That forced him to traverse the pit lane and receive a black and white flag for failing to follow the race director’s instructions on pit entry.
Midway through proceedings, Charles Leclerc rose to the top of ths standings on a set of soft tyres, logging a 1:38.130s.
Soon after, race runs became the focus of the session.
A mistake from Fernando Alonso saw the Aston Martin driver overcook pit entry, skating beyond the apex into the lane.
The Spaniard weaved his way through the tyre barriers before executing a neat flick spin in the run-off – narrowly avoiding recovery vehicles – before doubling back on to the pit entry, where he returned to the Aston Martin box.
Piastri had a similar incident, though he didn’t slalom his way through the tyres like Alonso and instead engaged reverse to get himself out of trouble.
With 13 minutes remaining, Logan Sargeant completed a qualifying run to log a 1:38.317s to shoot up to second.
His Williams team-mate went fastest soon after, a 1:37.229s that left Alex Albon fastest with 10 minutes remaining.
A locked brake into Turn 6 cost him time on his flying lap and lost some 0.2s in the middle sector of the lap as a result.
The Mexican completed the lap, a 1:37.138s that saw him fastest only briefly as Verstappen managed a 1:36.660s just seconds later.
The order changed dramatically, with some unusual names popping up towards the top of the standings.
That included Kevin Magnussen in second fastest inside of five minutes of the chequered flag, while Esteban Ocon sat fourth for Alpine.
Piastri then scorched to the top of the timesheets with 1:36.629s. In the other McLaren, Lando Norris was even faster through the first two sectors but abandoned the lap to remain 15th.
Verstappen improved on his earlier best but still 0.03s slower than Piastri, with Perez a further 0.03 further back in third.
Hulkenberg joined his Haas team-mate towards the top of the timesheets as Lance Stroll went fastest in the final minute of the session.
The flag fell soon after, leaving the Aston Martin driver fastest from Piastri, Verstappen, and Perez.
Daniel Ricciardo was ninth best, his 1:37.238s more than seven-tenths clear of his RB team-mate Yuki Tsunoda in 12th.
Sprint Qualifying now follows, beginning at 17:30 AEST.